↪Neb Flattery will get you nowhere, alas. I have no idea. But the Fermilab videos with Don Lincoln seem to have the mark of truth to them. I'd venture a guess, but I know the subject is too tricky for guesses. What I get, though, is that the mass does not change, and is always the rest mass. I think he offer lins to other videos that expand on this. — tim wood

Thanks Tim. I did look at some of his other videos. Being from Fermilabs, I tend to think he's quite possibly right. I'm on a physics forum. I might ask the question there.

Small point: relativistic mass a convenient fiction; there's only rest mass, here:
https://www.youtube.com/watch?v=LTJauaefTZM — tim wood

Hi Tim, Interesting comment. I watched that video. I had always thought that very fast particles increased in gravitational mass. But apparently not so. As you seem to know a bit about this, can I ask a question that's a bit off the subject of the OP?

I had assumed that, if you lift a weight against the force of gravity, its gravitational potential energy increases by mgh and therefore its mass increases by mgh/c^2. Is that the case? Whatever provided the energy would have a corresponding decrease in mass to compensate.

Likewise, if you accelerate a particle, you add energy, 0.5mv^2. Does its mass increase by 0.5mv^2/c^2?

That it's a worrying possibility is lost to no one — TheMadFool

It doesn't worry me in the slightest.

I know I exist and I know I experience perceptions, phenomena. Those perceptions aren't random (like white noise), but have patterns. The patterns allow me to interpret them as a 4-dimensional world which is in a lot of ways consistent and to some extent predictable in all those 4 dimensions.

Producing this mental picture of a 4-d world involves interpretation of my perceptions.

Now, what I can't know is the source of those perceptions. Do they come from a world like the one in my mental picture, one which contains other people who are conscious just like me? Or do they arise in some other way, like a computer feeding stimuli into a brain in a vat?

I can't know that, and I don't need to know that. It makes no difference to me either way. It won't change my experiences or the way or feel about those experiences or the value to me of those experiences. And it won't change how I react to those experiences.

One might think that, if I assume other people aren't independently real, I would treat them badly. But I know that, if I do treat them badly, people will treat me in ways that I don't like. It makes no difference whether those people are independently real or not.

I try to get the maximum pleasure out of my existence. I would go about that exactly the same way whether or not other people are independently real - whether or not the world I perceive is independently real.

That describes doubt but doesn't explain its existence. — TheMadFool

Good point. The original question was 'How did doubt begin?'

I do tend to think that the answer to that is implicit in what I said, though. Animals need to make decisions in order to survive. Those that can't just die out. Decision making requires reasoning - like the bird deciding whether it's safe enough to come and get the bread from my hand. Good reasoning, in turn requires an assessment of the probability of the correctness of suppositions - 'How likely is it that I will survive the encounter?'

So doubt evolved right from the beginning of animal life (in the Cambrian or just before) along with other evolved behaviors. Basically it has always been there and animal life would be impossible without it.

I think the word 'meaning' has different meanings to different people. We don't seem to have a generally accepted definition here.

When I was a youth, it worried me that my life didn't seem to have any meaning. By that, I think I meant something like 'purpose'.

After a year or so of soul searching, I came to accept that it in fact didn't have any meaning. But, far from making me more depressed, I realized that that was actually a good thing. If my life had a purpose, then I would feel under some sort of obligation to fulfill that purpose. If it had no purpose, then I was free to do whatever I wanted with my life.

Some might think that that would then lead me to be a totally depraved, immoral, self-centered seeker of immediate pleasure with no regard for anyone else. But it didn't, because I realized that ignoring the needs of others in the long run would make life worse for me. I wanted to have friends. What I chose to do with my life was to get as much pleasure and as little pain as possible from it. And this in fact led to the same sort of life that people with morals lead.

This is what I think.

All knowledge has an associated probability of being correct. For the knowledge that I exist, I would put it at 100%; for the knowledge that others exist in the way I do, I would put it at 90%; for the knowledge that more than a quarter of the population of Europe died in the great plague, I would put it at maybe 60%; for the knowledge that I will die before I’m 70, I would put it at about 10%; and so on.

All these probabilities are of course subjective and approximate, but they reflect my degree of confidence that the knowledge is correct. The difference between any of the above probabilities and 100% is the doubt associated with that knowledge.

For me, all knowledge other than that I exist and have certain experiences is less than 100% and therefore has some doubt attached. Doubt is a natural and inevitable part of thinking and awareness.

I don’t believe it’s just humans that think and doubt. Watch a wild bird approaching food when there is possible danger present. It isn’t sure whether it’s safe enough to take the risk. The probability that it’s safe enough is less than 100%. Of course, it can’t count to 100, but it makes its decision based on an intuitive assessment of the probability in conjunction with its degree of hunger. Even a fly will exhibit the same sort of behaviour.

Does a fly doubt? I believe so. What’s more, doubt is a form of reason, so a fly reasons – and quite effectively for its purposes.

Thomas knew that Jesus had died. Other disciples told him that they had seen him alive since he died. Thomas’ reaction was to doubt what they told him. To him, the probability that they were right would have been less than 100% (though greater than 0%). To put it at 0% or 100% would have displayed an inability to reason well.

Jesus scorned Thomas for doubting, for not being 100%. But no thinking person would or could be 100%. Christianity, like many religions, requires faith. Hebrews 11:1 defines faith as being sure of what we hope for and certain of what we do not see. ‘Certain’ means 100%. The choice is to listen to your reason or to have faith (100% certainty). But most humans can’t completely abandon reason any more than that bird or the fly can. Nor can they voluntarily be 100% certain of something without totally compelling evidence. This implies that faith (and therefore salvation) are impossible for most.

Hi. This is my first post in this forum. I’m not a philosopher, so please excuse me if I talk rubbish.

The posts so far in this thread have mostly treated this as a philosophical question. To me, the question is more interesting as a scientific one and I tend to think it was originally asked with a scientific answer in mind.

I think what it is asking is ‘Why are there electrons and protons, quantum fields, space-time and so on – physical things that make up our universe?’ People have suggested that there can’t be nothing because even ‘nothing’ is a mental construct and therefore ‘something’. I tend not to take the Platonic view that all possible mental constructs exist, even in the absence of any mind to construct them. So, to me, the absence of space-time and the fields that we understand to make up the universe would leave ‘nothing’. Nothing is what there would be if the big bang hadn’t happened. And this nothing is, I think, the nothing that the original poser of the question had in mind.

So I will treat it as a scientific question. As such, however, I really don’t think we have an answer to the question and it might well be that, being unable to see outside our universe, we will never have the information we need to get an answer.

As an analogy, consider a meson produced in a particle collision. It begins its life in the collision, lasts a small fraction of a second, then decays into something else and no longer exists. We don’t really know what a meson is apart from a few observable properties like its mass, velocity, charge, spin etc. Beyond knowing that it is made from two quarks, we can’t tell if it has more detail inside it than that. But suppose, hypothetically, that the meson was a self-contained universe a bit like ours, which evolved thinking beings (admittedly on very compressed space and time scales). Their universe would have a beginning and an end. They might wonder about why is existed (‘why is there something rather than nothing?’) and what caused it to exist. We know that is was caused to exist by the collision of two other particles. But the minds in the meson universe could never know that because they can’t see anything outside their universe (beside it, before it or after it). However much they observed and analysed their universe and however much their philosophers pondered it, they could never know that it existed because some human did an experiment with a particle accelerator.

Just like the meson people, we are quite possibly in a universe which is part of something bigger, but which we can never know anything about. It would then seem to be impossible to answer the question ‘why is there something rather than nothing?’

If we’re not part of something bigger, thinking about why the universe came into existence 13.8 billion years ago is too mind-boggling for me. If we are part of something bigger, there might be a reason why the universe exists. But then there is still the question of why the bigger universe exists. And so on ad infinitum.

Of course, the above could all be wrong. It could be that, through scientific investigation, we are starting to get an inkling of why there is something. Particle – anti-particle pairs come into existence from nothing and for no apparent reason throughout space all the time (quantum fluctuations). They have a certain energy/mass and, by the uncertainty principle, can only exist for a very short time before annihilating each other back to nothing again. The more energy such particles have, the shorter the time they can exist. If they have no energy, however, they can exist for ever. It has been argued that the positive particle/field energy of the universe exactly cancels the negative gravitational energy, so the universe might have exactly zero energy and thus could be a quantum fluctuation that lasts for ever. Maybe such quantum fluctuations just have to happen, even when there is nothing for them to happen in. Who knows? We can’t perform an experiment to test the idea unless we have a bit of ‘nothing’ to test it in. And we can’t get away from the fields that make up the fabric even of ‘empty’ space.